Students can go through AP State Board 10th Class Physical Science Notes Chapter 3 Refraction of Light at Plane Surfaces to understand and remember the concept easily.
AP State Board Syllabus 10th Class Physical Science Notes Chapter 3 Refraction of Light at Plane Surfaces
→ The process of changing speed when light travels from one medium to another medium is called the refraction of light.
→ Absolute refractive index = \(\frac{\text { Speed of light in vacuum }}{\text { Speed of light in medium }}\) ⇒ n = \(\frac{\mathrm{c}}{\mathrm{v}}\)
→ Relative refractive index, n21 = \(\frac{v_{1}}{v_{2}}=\frac{n_{2}}{n_{1}}\)
→ Snell’s law is given by, n1 sin i = n2 sin r.
→ The angle of incidence at which the light ray travels from denser to rarer medium grazes along the interface is called the critical angle of that interface.
sin C = \(\frac{n_{2}}{n_{1}}\)
where n1 is the refractive index of the denser medium and n2 is the refractive index of the rarer medium.
→ If the angle of incidence is greater than the critical angle, the light ray is reflected into the denser medium at the interface. This phenomenon is called total internal reflection.
→ Example of denser medium: Glass.
→ Example of a rarer medium: Air.
→ When the light travels from rarer to a denser medium, it bends towards the normal.
→ When the light travels from a denser to a rarer medium, it bends away from the normal.
→ Optical fibers work on the principle of total internal reflection.
→ Mirages are formed due to total internal reflection.
→ The refractive index increases with height.
→ Total internal reflection is the main cause for the brilliance of diamonds.
→ Light travels at a speed of 3 × 108 m/s.
→ The Refractive index depends on the following factors :
- Nature of material
- The wavelength of light used.
→ When the refractive index of glass is \(\frac{3}{2}\), then the speed of light in glass is equal to 2 × 108 m/s.
→ Laws of refraction :
- The incident ray, the refractive ray, and the normal interface of two transparent media at the point of incidence lie in the same plane.
- During refraction, the light follows Snell’s law.
→ A coin kept at the bottom of a vessel filled with water appears to be raised and a lemon kept in the water of glass tumbler appears to be bigger than its size due to refraction of light.
→ Fermat’s principle states that the light ray always travels in a path that needs the shortest possible time to cover the distance between the two points.
→ Speed of light changes at the interface of two media.
→ The angle between the incident and normal ray is called the angle of incidence.
→ The angle between normal and refracted ray is called the angle of refraction.
→ The angle between normal and emergent rays is called the angle of emergence.
→ The formation of mirage is the best example where the refractive index of a medium varies throughout the medium.
→ Refraction: The process of changing speed when light travels from one medium to another is called the refraction of light.
→ Incident ray: The ray which is an incident on a surface is called an incident ray.
→ Refracted ray: The ray which refracted from a surface is called refracted ray.
→ The angle of Incidence: The angle between the incident ray and normal ray is called the angle of incidence.
→ The angle of Refraction: The angle between refracted ray and normal ray is called the angle of refraction.
→ Absolute refractive index: The ratio of the speed of light in a vacuum to the speed of light in the medium.
→ Relative refractive index: It is the ratio of the refractive index of the second medium to the refractive index of the first medium.
→ Snell’s law: It is the ratio of the sine of the angle of incidence to the sine of the angle of refraction.
→ Critical Angle: The angle of incidence at which the light ray travels from denser to rarer medium grazes along the interface is called the critical angle of that interface.
→ Total internal reflection: When the angle of incidence is greater than the critical angle, the light ray is reflected into the denser medium at the interface. This phenomenon is called total internal reflection.
→ Mirage: Mirage is an optical illusion where it appears that water is collected on the road at a distant place but when we get there, the road is dry.
→ Shift: The distance between incident and emergent parallel rays is called shift.
→ Optical Fibre: An optical fiber is a very thin fiber made of glass (or) plastic having a radius of about a micrometer (10-6 m).
→ Medium: A substance through which light passes is called medium. The medium has more optical density.
→ Denser Medium: The medium which has less optical density.
→ Interface: A point where two things meet and interact is called an interface.
→ Fermat’s principle: The light ray always travels in a path that needs the shortest possible time to cover the distance between the two given points.
→ The angle of emergence: The angle between normal and emergent rays is called the angle of emergence.
→ Light pipe: A bunch of optical fibers is called a light pipe.
→ Mass density: Mass per unit volume is called mass density.
→ Ray: The straight-line path along which the light travels in a homo¬geneous medium is called a ray. It is represented by an arrowhead on a straight line, the arrowhead gives the direction of propagation of light.
→ Beam: A number of rays combined together are called a beam
Williboard Snell Van Royen (1580 – 1626):
- He was a Dutch astronomer and mathematician.
- His name has been attached to the law of refraction of light.
- In 1815, he planned and carried into practice a new method of finding the radius of the earth by determining the distance of one point from the parallel of latitude of another by means of triangulation.
- He was famous for bis Snell’s law related to the refraction of light.